Electric heating system



April 14, 1925. 1,533,247

H. A. HANDS ELECTRIC HEATING SYSTEM Filed NOV. 14 1922 WITNESSES: INVENTOR I flowapck Afiaqa J m g BY ATTORNEY atenteol Apr. 1,

r M w 9 owann a. HANDS, or .SWISSVALE, PENNSYLVANIA, assienoa 'ro w i House ELECTRIC & manuraoruamc COMPANY, A conroaa'rron orrEmvsYL- VANIA.

ELECTRIC HEATING SYSTEM.

To all ivhom it may concern:

' Be it known that I, HOWARD A. HANDS, a citizen of'the United States, and a resident of Swissvale, in the county of Allegheny.

and State'of Rennsylvania, have invented a new and useful Improvement in Electric Heating Systems, of which the following is a specification.

My invention relates to control systems and particularly totemperature-control systems.

The object of my invention is to provide a. relatively simple, inexpensive and rugged system comprising a minimum number of parts for controlling the temperature of an electrically heated device. [In practicing my invention, I provide a heating element, the energization of which is controlled by a motor-operated snap switch. A plural-pole fluid circuit interrupter controls the energization of the 'mo tor, and a closed-circuit variable resistance cell thermally controlled by the heating element,.controls the operation of the circuit interrupter by variably energizing a heating coil operatively associated therewith.

The single figure of the accompanying drawing is a diagrammatic representation of a temperature control system embodying my invention.

A suitable supply of electric energy is provided by a pair of conductors 11 and 12. An electric heating element 13 has one of its ends electrically connected to the supplycircuit conductor 12 by a conductor 14 and has its other terminal connected, by. a conductor 15, to one of the terminals of a snap switch 16.

The snap switch 16 comprises a suitable base 17 and a plurality of terminal contacts 18, 19, 21 and 22, mounted in symmetrically spaced positions thereon. A contact-bridging member 23 is rotatably mounted on the base 17 to selectively engage and electrically connect the opposing pairs of contact terminals 18'-21 and 1922. A small motor 24 is mechanically connected to the contact-bridging member 23 by a shaft 25. While I have illustrated a direct connection between the motor and the contact bridging member, itis to be understood that this connection maybe made in any suitable or desired manner, either as illustrated or by means of a trainof gear wheels.

One terminal of the motor 24 may be electrlcally connected to the supply-circuit conductor 12 by conductors 26 and 14, as illustrated in the drawing. The two contact-terminal members 21 and 22 of the switch 16 are' electrically connected together and to the supply-circuit conductor 11 by a conductor-27.

The energization of the motor 24 is controlled by a fluid circuit interrupter 28 com- PIISlIlg an elongated closed evacuated tube 29 of a suitable insulating material, such as glass or quartz. The tube 29 is provided with a plurality of spaced constricted portions 31' and 32. Terminal leads 33, 34 and 35 extend into the tube 29 through the wall thereof, in spaced position, the terminal leads 33 and 35 being located adjacent to the ends of the tube and the terminal lead 34 being located intermediate the two constricted-portions 31 and 32. A body 36 of a suitable electric-conducting fluid, such as mercury, is placed within the tube, the quantity being such that, with the tube in a substantially vertical position, the, leads 33 and 34 will be electrically connected thereby.

The terminal lead 33 is electrically connected, by a conductor 37, to the contact terminal 19 of the switch 16. The terminal lead 34 is electrically connected, by a conductor 38, to one terminal of the motor 24. The terminal lead 35 is electrically connected, by a conductor 39, to the conductor 15 which, in effect, connects it to one of the ter-.

minals of the heating element 13 and also to the contact terminal 18 of the switch 16.

A heating coil 41 is operatively associated with the circuit interrupter 28, being wound around the constricted portion 31 of the tube 29. A source of electromotive force for energizing the heating coilf41 may comprise a transformer secondary winding 42 of rela-' tively low voltage which is energized by a primary winding 43 permanently connected to the supply-circuitconductors 11 and 12.

The energization of the heating coil 41 iscontrolled by a closed-circuit, variable-resistance cell 44 which may comprise a metallic tube 45 within which is placed a quantity 46 of a suitable electrolyte, such as silver chloride or potassium nitrate, which has a negative temperature coefiicient of resistance with-increasing temperature.

One terminal of the heating coil 41 is electrically connected to the metal tube 45 by a conductor 47, and its other terminal is electrically connected to one terminal of the winding 42 by a conductor 48. The

other terminal of the winding 42 is electrically connected by a conductor 51, to anelectrode 49 located within the tubular member 45 and operatively engaging the electrolyte 46. The cell 44 is more particu larly described and claimed in Patent No." 1,406,352, to P. E. Demmlcr; dated Feb. 14,

The illustrated positions of the various elements of the system are such as occur when the temperature of the heating element or of the device heated thereby is rela tively low and the system is about to operate to again close the circuit through the heating element. If it be assumed that the supply-circuit conductors 11 and 12 are suitably energized, a-circuit is established as follows: from supply-dircuit conductor 11 through conductor 27 to terminal 22,

contact-bridging member 23, terminal 19, conductor 37, lead 33, fluid 36, lead 34, conductor 38, motor 24, and conductors 26 and 14 to supply-circuit conductor 12. This energizes the motor 24 which operates tomove the contact-bridging member 23 from the position illustrated in the drawing to a position substantially at right angles thereto, which operation interrupts the circuit through the motor and closes an energizing circuit through the heating element 13 substantially' as follows: from supply circuit conductor 11, conductor 27, contact terminal 21, bridging member. 23, contact terminal 18, conductor 15, heating element 13 and conductor 14 to supply-circuit conductor 12.

The cell- 44 is under the thermal control of the heating element 13 or of the device heated thereby, and its temperature is, therefore, raised substantially in accordance with the temperature of the heating element 13 or of the device heated thereby.

At a predetermined temperature of the cell 44, and, therefore, of the heating element 13, the electrolyte in the tube. 45 fuses and the resistance thereof becomes relatively very small. A relatively large current is thereby permitted to flow through the cell 44 and, therefore, through the heatingcoil 41. The heat generated by the heating coil 41 causes a vaporization of a portion ofthe conducting fluid located above the constricted portion 31, whereby the fluid located above the constricted por-,

tion is forced upwardly in the tube 29, which is maintained substantially stationary, until it operatively connects the terminal'leads 34 and 35 while, at the same time,

the previously existing electrical connection between the terminal leads 33 and 34 is broken. This action. closes an energizing circuit to the motor 24, substantially as follows: from supply circuit conductor 11 through conductor'27, contact terminal 21, bridging member 23, contact terminal 18, conductor 15, conductor 39, terminal lead 35, conducting fluid 26, terminal lead 34, conductor 38, motor 24 and conductors 26 and 14 to the supply-circuit conductor 12. The energized motor, therefore, operates to move the bridging member 23 to substantially the position illustrated in the drawing, whereby the circuit through the heating element 13 is interrupted, as is also the energizing circuit through the motor 24.

The temperature of the heating element 13 and of the .device heated thereby falls, whereby the resistance of the variable-resistance cell 44 is again caused to increase, resulting in a decrease in the current traversing the heating coil 41. After a predetermined lapse of time, determinedmore particularly by the rate of cooling of the fluid circuit interrupter 28 after the reduction of the current traversing the coil 41, the conducting fluid 36 in the tube 29 again resumes the position indicated in the drawing, connecting theterminal leads 33 and 34. An energizing circuit is, therefore, again established through the motor 24 which operates to close the circuit through the heating element 13, as hereinbefore described. 1

Various changes in detail and arrangement may be made without departing from the spirit and scope of the invention, and such modifications are intended to be covered by the appended claims.

I claim as my invention:

1. In a temperature-control system, in

combination, a heating element, a motoroperated switch for controlling the energization of said heating element, a fluid circuit-interrupter, for controlling the operation ofsaid motor, and a closed-circuit" variable-resistance means for controlling said fluid circuit-controller.

2. In a temperature control system, in combination, a heating element, a motoroperated switch for controlling the energization of said heating element, a fluid circuit-interrupter for controlling the operation of said motor, and a closed-circuit variable-current means thermally influenced by said heating element for actuating said fluid circuit interrupter.

3. In a temperature-control system, in combination,-a heating element, a motor-' operated switch for controlling the energi zation of said heating element, a fluid circuit-interrupter for controlling the operation of said motor, a heating coil operatively associated with fluid circuit-interrupter to actuate the same, and a variable-resistance cell, under the thermal influence of said heating element, for controlling the energization of said heating coil.

4. In a temperature-control system, in combination, a heating element, a motoroperated switch for controlling the energization of said heating element, a fluid circuit-interrupter for controlling the operation of said motor, a heating coil operatively associated with fluid circuit-interrupter to actuate the same, and a variableresistance cell, under the thermal influence of said heating element for permitting the energization of said heating coil to eflect the closing of an auxillary circuit through said circuit-interrupter and said motor, whereby theinterruption of an electric current traversing said heating element is effected. I 2 v 5. In a temperature-control system, in combination, a heating element, a motoroperated snap switch for controlling the energization of said heating element, a three-pole, substantially stationary, fluid circuit-interrupter for controlling t e energization of the motor of said snap switch, and a closed-circuit variable-resistance terrupter.

6. Ina temperature-control system, in combination, a heating element, a motoroperated snap switch for controlling the energization of said heatin three-pole, substantially stationar fluid circuit-interrupter for controlling t e energization of the motor of said snap switch, a heating coil operatively associated with said fluid circuit-interrupter to actuate the same, and a variable-resistance cell permanentl connected in series circuit relation to said eating coil for energizing said heating coil. I

Ina temperature-control system, in combination, a heating element, a motoroperated snap switch for controlling the energization of said heating element, a three-pole, substantially stationar fluid circuit-interrupter for controlling t e energization of the motor of said snap-switch, a heating coil operatively associated with said fluid circuit-interrupter to actuate the same, and a variable-resistance cell for permitting the energization of said heating coil inversely in accordance to the temperature of said heating element. 8. In a temperature-control system, in combination, a heating element, a motoroperated snap switch for controlling the energization of said heating element, a three-pole substantially stationary, fluid circuit-interrupter for controlling the energization of the motor of said snap-switch, a heatin coil operatively associated with said fluid circuit interrupter, and a variablemeans for actuating said fluid circuit in-' element, a

resistance cell under the thermal control of said heating element for permitting the energization of said heating coil to efl'ect operation of said fluid circuit in'terru ter 5 upon the occurrence of a predetermlne temperature in said heating element.

9. In a temperature control system, in combination, a heating element, a motoroperated switch for controlling the energi- 7 zation of said heating element, a fluid cirwit-interrupter for controlling said switch motor and comprising a closed elongated tube of insulating material, three spaced electric-circuit terminals extending into said tube and a quantity of an electric-conductingfluid in said tube normally operatively engaging two of. said terminals, and thermally controlled electric means for interrupting the initial circuit in said tube and for closing another circuit therethrough upon the occurrence of a predetermined temperature in said heating element.

10. In a temperature controlling system, in combination, a heating element, a motoroperated switch for controlling the energization of said heating element, a fluid clrcuit-interrupter for controlling said switch motor and comprising a closed elongated tube of insulating material, three spaced electric-circuit terminals extending into said tube and a quantity of an electric-conducting fluid in said tube normally operatively engaging two of said terminals, a heatin coil operatively associated with said flui. circuit interrupter, and a variable-resistance cell foreontrolling the energization of said heating coil.

11. In a temperature control system, in combination, a heating element, a motoroperated switch for controlling the energization of said heating element, a fluid circuit-interrupter for controlling said switch motor and comprising a closed elongated tube of insulating material, three spaced 106 electric-circuitterminals extending into said tube and a quantity of an electric-conducting fluid in said tube normally operatlvely engaging two of said terminals, a heatlng coil operatively associated with said flu1 circuit interrupter, and a variable-resistance cell thermally controlled by said heating element to cause operation of said motoroperated switch to interrupt the clrcult through said heating element upon the occurrence of a predetermined temperature therein.

In testimony whereof, I have hereunto subscribed my name this 4th day of N ovember,1922. v

noWaRD A. HANDS. 

